Cartridge feeding mechanism for automatic guns



Nov. 16, 1948. W HAM|LTON- 2,454,251

CALUR'IRIDGEv FEEDING MECHANISM ,FOR AUTOMATIC GUNS Filed Jan. 11, 194el 9 sheets-sheet 1 w. HAMILTON A2,454,251 GART'RIDGE FEEDING MECHANISMFOR AUToMATIp GUNS 194e 9 Sheets-sheet 2 Nov. 16, 1948.

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CARTRIDGE FEEDING MECHANISM FOR AUTOMATIC GUNS Filed Jan. l1, 1946 9Sheets-Sheet 5 Nav. 151948.

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Nov. 16, 1948; w. HAMILTON 2,454,251

l CARTRIDGE FEEDING MECHANISM FOR AUTOMATIC GUNS Filed Jal). l1, 1946sheets-Sheet 8 ymffmm;

W. HAMILTON CARTRIDGE FEEDING MECHNISM FOR AUTOMATIC GUNS Filed Jan. 11,1 946 9 Sheets-Sheet 9 NNW Sv umm. mmm mi. umn NS @y i f Nw @3MWQ/.MP/MM www Patented Nov. 16, 1948 CARTRIDGE FEEDING MECHANISM FonAUTOMATIC GUNS Wallace Hamilton, Albany, N. Y.

Application January 11, 1946, Serial 120.640.447

, 4 Claims.

This invention relates to improvements in the structure of automaticguns of the type which use belt ammunition and which are capable ofcontinuous ring. The invention hereinafter cle-- scribed relatesespecially to 20 mm.` guns such as are suitable for use in aircraft. Itis an object of the invention to` provide a gun of this type which canbe operated by remote control, which is capable of rapid fire of theorder of 800 to 1,000 rounds per minute, and in which the mechanism isrelatively simple, reliable, durable and self-contained.`

For a more complete understanding of the invention, reference may be hadto the following description of an embodiment thereof and to thedrawings of which:

Figure 1 is a side elevation of a 20 mm. gun embodying theinvention.

Figure 2 is a plan view of the same.

Figures 3 and 4 are a section of the gun taken on the line 3-#3 ofFigure 2 but on a larger scale. the parts being shown in positionsoccupied when the gun is ready to fire.

Figure 5 is a section on the line 5-5 of Figure 1.

Figure 6 is a ure 3.

Figure '7 is a section onthe line 1-1 of Figure 3.

Figure 8 is a fragmentary sectional view on the line 1 1 of Figure 3,the bolt being retracted.

Figure 9 is a 'portion of Figure 3 shown on a larger scale and with someparts of the feeding mechanism shown inelevation.

Figure 10 is a side elevationV of the striker assembly with certainparts thereof shown in section.

Figure 11 is a part of Figure 9 showing the positions of some of theWorking parts at a moment during recoil. t

Figure 12 is a part of Figure 9 showing the positions of some of theWorking parts. near the end of recoil.

Figure 13 (sheet 1) is a fragmentary section on the line 1--1 of Figure3, some parts being shown in plan. n

Figure 14 (sheet l) is a fragmentary sectional view in a vertical planeof a modified form of trigger mechanism. i

Figure l5 is a sectional vievv of the buffer mechanism.

Figure 16 is a front elevation of the'buffer mechanism. i v

Figure 17 is a plan view of the escapement latch of the feed mechanism.

section on the line 6 6 of Fig- Figure 18 is an exploded View of thebreechblock assembly.

Figure 19 is a sectional vievv of the rear portion of the bolt andstriker extension.

Figure 20 is a fragmentary sectional vievv of the breechblock lockingmechanism in a plane similar to that of Figure 3.

Figures2l and 22 are similar to Figure 20 but with the parts shown indiiferent positions of operation.

Figure 23 is a portion of Figure 4 but shown on a larger scale with theparts in a different position in the cycle of operation.

Figure 24 is a rear end elevation of a valve in the gas cylinders. Y

Figure 25 is an elevation of one of the side plates for the clutch androtor housings.

Figure 26 is a plan view of a cam plate for the extractor.

Figure 27 is a section on the line 21-21 of Figure 26.

Figure 28 is a partial rear elevation of the gun, a portion being shovvnin a section on the lin 28-28 of Figure 5, 'A -v Figure 29 is a sectionon the line 29-29 of Figures l and 3.

Figure 30 is a section on the line 313-30 of the Figures 1 and 3.

Figure 31 is a, section on the line 3I--3I of Figures 1 and 3.

Figure 32 is a section on the line 32-32 of ures 1 and 3.

Figure 33 is a section on the line 33--33 of Figure 31.

Figure 34 is a section on the line 34--34 of Figures 1 and 3.

Figure 35 is a section on the lines 35-35 of Figures 1 and-3.

Figure 36 is a section on the line 36-38 of Figure 1.

Figure 37 is a section on the line 31-31 of Figures 1 and 4.

Figure 38 is a section on the line 38-38 of Figures 1 and 4.

Figure 39 is an end elevation of the feed sprocket Wheel.

Figure 40 (sheet 2) ris a longitudinal section of the clutch housing. l

Figure 41 is a longitudinal section of the vrotor housing. l

Figure 42 is a side elevation of the rotor roll guide.

Figure 43 is a perspective View of the member.

As indicated in Figures 1 and 2, the gun em- Figboit 'Stop o bodying thepresent invention comprises a barrel or tube D connected through recoilmechanism, generally indicated as 5|, to trunnion blocks 52 which arepart of a bracket 53 mounted on a cradle 54, Screw-threaded to the rearend of the barrel or tube 5u is a receiver body 55 which contains mostof the working parts of the gun, and-consistsiofaneelongated steelbloxlyhaving sidewalls 256 and i512 and a vremovablecover 59. The rearportion of the receiver is slidably supported by a receiver guide Ri(Figure 29) which is secured to the cradle 5ft. yA troughshaped receiverslide 6| (Figures3,Li5,`6land,2,9) is secured within the rear portion ofthe-receiver sufciently above the bottom thereof'togfguideethe boltassembly as hereinaftervdescribed. At the rear end of the receiverbody555'is the 'buiferassembly 62.

' Gas cylinders Power for unlocking the breech and for operating thefeed mechanism is obtained :by ,utilizing gas `pressure fromthegpropellin'g gases .behind the projectile. A small-portion offthesegases is sllpplyingthefmotive power ftorfthe reed 'mechanism. VItcontains la1pii`ston' 'M1-'to which is secured ya connecting'rod 7G. Byreciprocationfthis rod, the 'feed 'mechanisrn isactuated "as hereinafterdescribed. rThe feed cylinder @8l-is screw- -threaidedto'tlheVvunlocking f'cy'linder f 6G, the latter ihavin'gl an: end -lwall I'18iwi-lich serves-jas alp-artitionhbetween the two cylinders. Thecylinders aire-securedto'the barrel orfftbe ill-'by "ai bracketAurearward.

piston 10 being in its forward position, the pis- 8D and are lockedagainst rotationlby'-akey82 grippedfby -the'lbracket'i t. 'ilThe piston"'l0 is ihollow and contains a plug 8s whichisslidably'tted isV slidablylltted'th'rough a central aperture' in the `end wall 18. The sleeve 8Shas {ahead 88 which engages'l'within -aislifdevalved The rear portion ofthe valve 9i) is slidably ttedin fthe yfeed 'cylinder i158 I:and 'iliasfa vertical 'Islet 92 (Fingiuev 24) in its rear end wall in which--thelsleeve -86 is'itte'd. iThe-'iffoiward Tportionfofthe valve 9U has asmaller diameter and? the forward -wall .hasfaverticalfsl-otffiitofreceive'f'th-e connecting rod 16. Rearward movement of thevalve toisimpartedtby the sleevett, @Fo'rwardemovement of the valve isimparted by a-angelbn the. rod We @which sengagesi'theforward wall ofthe valve. The bottom of the valve=attherear fend thereofisfsla'bbedprlto form 'a' port feiwhich registers with the port 64whenthevva'lve'lisikin fits aforwar'd iposition. s-Movement of the"valve to the rear cuts on" the portfl. .ffAf'slot'lalong the topi o`fthe "Valve maintains :free .passage of gas from the interior of thevalve to .the'rest Ward from the end wall YS, engages in the-'slot :92:to iprevent 'any rotation :of .the -valve *590.

Within the forward 4part of the unlockin'gscylinder eiis sasgas :einig llo2rnavingsa1zpair :off small ton 'M being in its rearward position, andthe 'gvalve)Sbeingfforward so that the port 98 regis- @terswith the port|34. When a projectile passes f theports-LSS-fand Eli, a blast ofhigh-pressure gas enters the chambers in the cylinders 66 and 68`through these ports. The unlocking piston is 'acts'through the sleevehead 88 to move the valve 99 so as to close the yport 64. This traps the`gas "which'has entered the chamber in the ycylinderii so that pressureis maintained on the piston -'M until thefeed mechanism is released foroperation' ashereinafter described. The last part ofthe forward movementof the feed piston "M causes the flange '96 topull the valve 90forwarcL'opening the port 64 to relieve residual pressure within thecylinderl 68. The springs |06 `and illrest'ore the-pistonsto theirnormal positions. The inertiafof the valve 2|] during thebrief'intervals of recoil iand lcounter recoil aids invitsproperoperation. Thus its-inertia during 'recoil tends to'give-'itrelative forward vmovement ensuring an openport Mito receiveexplosion gases from'the -tube orbarrel 5U, and likewise, its inertiaduring counter recoil tends to-'give itrearward movement-which isdesirable at-this stage of Ithe cycle.

QBreechbZoclc assembly 'Welded or. otherwise secured to the rear end oftheiunlocking sleeve F2 is a yoke ||2 which engages the forward ends ofa pair of push rods or tappets fil-4. The tappets kbear againstthefforward ends of a U-shaped breechblock slide||6 (Figure 18).@Sli'dab'ly fittedl in the space between the arms of the slide H6 is thebottom plate H8 -of the bolt |20. :Projectinglaterally from the forwardend of the bottom plate ||8 are feet |'8 lwhich atltimes 'engagethe'forward ends of the slidefllfbetween the tappets IM. TheA body ofthevbolt |29 is generally cylindrical with a wid- 'ened intermediatepart |22-having a transverse thrust surface |24 -lwhich bears againstthe breechblock Alocky ['26 whenthe bolt is locked for firing.Theportion of. the bolt to the rear of the thrust element |22 is squared(Figures 30 and 31) fandthe fupper part of lthis'rear portion is outaway at` |21, forming a recess to receive a breechblock lock |26 and astriker release |28, both of whichimembers straddle the bolt at thispoint, the forward edge of the lock |26 bearing directly against thethrust surface |24 of the bolt. The bolt-.'I'ZU-has a bore extendingfrom end to end thereof but -having three Aportions of differentdiameters, as indicated in Figure 3. The portion of .smallest vdiameteris at the .forward end of the bo1t,1this diameter being just largeenough to receive the shank of a ring pin |30 which has 'ahead-|32within the "mid portion'of the vbolt bore, This mid portion alsocontains a striker pin 1 |534 :(Fi'gurel) having .a head |36 behindwhich is a helical compression spring |38 surrounding a portion of the-pin |34. The rear'portion of the pin eXtendssldably througha'cylindrical spring retainer |40,-the endportion of the pin beingscrew-threaded into a'cylindrical striker pin extension `|42 (Figure19).` -In order to prevent -unscrewing of the striker pin when in use,the rear end of the pin is transversely grooved as at |44 to registerwith the rounded forward end of a vertical slot |46. Fitted in the slot|46 is a firing pin key 48 the rounded forward edge of which also fitsin thegroove |44 in the end of the striker pin to keep the pin fromturning. TheA firing pin key |48 projects up through a slot |50 in thebolt |20 and thus keeps the striker extension |42 fromA turning. lThisslot is long enough to permit a limited relative'movement between thestriker assembly and the bolt (Figures 20-22) As hereinafter described,the upper portion of the key|48which projects above the bolt is en-'gageable by the sear to prevent firing of the gun until the key isreleased.

The spring retainer |48 is provided with a small l lug |52 which entersabayonet slot |54 (Figure 19) in the bore of the bolt to anchor thespring retainer with respect to the bolt. The spring |38 is undercontinual compression between the retainer |40 and the striker head |36so that the striker head |36, pin |34,andextension |42 are constantlypressed forward.

The `breechblock slide `||6 is made with upstanding blocks |56 separatedby a channel |51 in which a portion of the bolt |20 slides. lIn thischannel is an upstanding cooking lug |58 `which projects up through aslot |60 (Figures 20-22) ,in the bottom of the rear portion ofthe boltto engage a shoulder |62 on the under side ofthe striker extension |42(Figure 10).` VThe slot |60 limits the relative rearward movement of theslide with respect to the bolt.` Relative forward' movement of theslidel is limited by the bottomY plate ||8 when the curved rear end ofthe plate `is engaged byzthe corresponding curved edge of each explosionis transmitted from the cartridge,

case to the receiver' through the bolt |20, and the lock |26, the key|66 andthe receiver key |68;

For the operation of the lock |26 inclined cam faces |12 are provided onthe upstanding parts |56 of the slide I6 to engage corresponding faces|14 on `the lock |26 when the slide moves lforward with respect to thebolt so as to elevatethe rear end of the lock into the locking positionshown in` Figure 20. The slide block |56 also has forward l cam faces|15 which are lower than the faces |12 and are engaged by correspondingcam faces |16 on the lock |26 to elevate the forward end of the lock |26to a lesser extent when the.v slide moves forward with respect tothelbolt-` y Thus` when the lock |26 is moved into locking position,

itwis bodily lifted as well as being tilted. By this: combination of abodily lift with the tilt to move the lock |26, a smaller` angle of tiltisrequired for.

the locking position. `This is advantageous because the thrust ofthebreechblock is horizontal and the tilt of ,the lock produces a verticalcomblock compresses the springs of the buler and' rebounds forward toram the new round into the firing chamber, pushing with it the slide H6.When the forward 'movement of the bolt is stopped by a bolt stop member11 (Figures 9 and 43), the slide continues by its momentum to itsforward relative position to lock the breechblock by camming up the lock|26. As

this locking movement of the slide is relatively ponent which should be`kept ata minimum(A Without the lift toreduce the tilt, a much longerlock would be necessary, which would-.be .objecslow compared with thenecessary velocity of the striker for effective impact on the firingpin, it is'necessaryto hold back the striker assembly during the lockingmovement of the slide since otherwise the striker would be slowed downto the speed of the slide by the engagement of the striker extension |42with the cooking lug |58, Hence a striker release member |28 is employedto engage the striker extension |42 and hold it back after the bolt hasbeen stopped until the locking movement of the slide I6 has been nearlycompleted. The striker release |28 ts loosely in a channel |18 in theunder side of the breechblock lock |26 and rides on the cutaway portionof the bolt (Figure 18). The striker release fits loosely in thisdepression just behind the thrust surface |24 of the bolt and isprovided with an abutment face |19 at its rear end to engage a shoulderon the forward endcam surfaces |14 on the lock |26, the spacing beingsuch that when the bolt stops its forward ramming movement, .the initialadditional forward movement of the slide cams the lock |26 up to itslocking position, but the release member |28 remains horizontal untilthe slide nearly reachesitsV forward limit. The nal fraction of slide`movement elevates the rear end of the re-,

lease member |28 and releases the striker which is then free to be movedforward by the spring |38 `to strike the rin'g pin |30.

Owing to the rapidity of the oscillations of the breechblock mechanismduring continuous firing, the: useful :life of thel striker spring |33is apt tobe very short, probably on account of longi tudinal waves setup in the spring itself. I have found that by packing the spring with aheavy, viscous grease, its useful life extended. l

The'ektractor consists of a single member |84 loosely embedded in alongitudinal groove in the bottom plate 8 of the bolt |20 (Figures 9 and12). i The extractor has trunnions |86 which are embedded -in a shorttransverse slot in the bottomV can be indefinitely plate ,l I .8.. Theextractor projects far enough for ward of the end of the `bolt for its;claw |86 to enter the extractor groove |96 of a rimless cartridge case|92 .when the latter is seated against the forward end face of the bolt.The fore portion of the extractor which terminates in the claw |86 isconsiderably wider thanthe shank of the extractor from which thetrunnions |86 project. As the extractor moves forward and back with thebolt, it rides on a cam plate |96 (Figures 9, 12, 26, 27, 30, 3l and 32)which rests on a bottom plate 896 of the receiver 55. The plateA |94, asclearly shown in Figurev 26, has three parallel cam tracks |66, 266 and262. As indicated in Figure 27, the middle trackstarts with a high pointat the rear end of the plate |95 and slopes to a low level whichcontinues to the forward end of the plate. The outer tracks |96, 262start to run at a low level from Athe rear end of the plate E94, thenslopev up to a high level which continues to the; forward end of theplate. A follower element 264 (Figure l2) near the narrow rear end ofthe extractor rides on the middle cam track 266. 'Two follower ele--ments 266 on the wider forward portion of the extractor ride on theouter tracks E65., 262'. The followers and tracks are so arranged thatwhen the follower 264 is riding uphill on its track 266', the followers266 are riding, downhill on their tracks, and vice versa., thusimparting rocking movements to the extractor about the axis of itstrunnions |66. These rocking movements occur when the bolt isappproaching or leaving its rearmost position.A When the bolt is in suchposition, the extractor claw i 68 isdown so that when moving rearwardlythe extractor releases the empty case, and when the bolt is moving,yforward to rain the next; round the claw can pass under the extractorrim of the cartridge case.,

It is evident that the camactu-.rated` rocking movement of the extractoris entirely positive-v It` and there is no spring to vibrate orbreak.occasionally happens that when the belt link holding the roundisr weak,the bolt4 strikes the base of the roundto ram it, into the firingchamber and the round jumps ahead of the bolt so.

of the round; by the momentum of the bolt and would jam the gun. Forthis reason a yielding:

plate 268 is set in flush in the forward end of v the cam plate |64. andis resilientlyupheldby a leaf spring 216. The cam followers-206 ride: on

the yielding plate: 2,68 when the bolt; approaches,

the forward end of its stroke so that. if the ex tractor claw |88 isthen against tliegbase ofthe round,A it can snap into the groove |96?without injury to the round or to itself and` permit the boltv tocomplete its rammi-ng stroke and reach its forwardmost, orbattery5'position, thus allow'- ing the slide and lock action to; lockrearward motion.

As indicated in Figure 7, the gun is adapted to use belt ammunitionwherein the rounds. are

frictionally held bymetal links. When ramming a round the1 bolt`projects. throughy the. link from which it, haspushed the round.After-the round, has been fired; the. empty-case returns to.,` the linkbefore it` is released the extractor.-v To;v facilitate the; reentry:ofithe-g cartridge-caser;

it Yagainst Sear cmdV trigger mechanism The sear 212 extends down fromthe forward end of the sear lever 2li" which is pivoted at its mid point2|6 (Figures 6, 9 and 1l.)v to the sear cover 2|8 so that the sear canbe moved into a position in front of the ring pin key |168 to preventfiring. The key |48 cannot move ahead of the sear, the limit of itsforward movement being shown in Figure 21. Hence the sear cannot catchbehind the key |48.

The sear cover 2|8 is supported in grooves in opposite side walls of thereceiver slide 6| and is secured in place by a pin 226 which passesthrough the side walls of the receiver slide and through two upstandingears 222 on the sear cover.

--The sear lever 2 Itis actuated by a trigger 224 whichy is vatransverse bar slidab-ly fitted in slots through the walls ofthereceiver slide and connected to the rear end of the sear lever by a stud225. One end of the trigger projects through a side wall of the'receiverbody 55, this projecting end having a crosshead 226 thereon with agroove s lidably fitted by a tongue 228 on a trigger slide 230 (Figure29). The trigger slide has a vertical stem 232l which ts the bore of agudgeon 234 at an intermediate vpoint of the solenoid lever 236. Thislever is hinged at one end 238 to a bracket 240 which carries thesolenoid 242 and is secured to the cradle 54. The free end 244 of thelever 236 is forked and engages in notches in the armature 246 (Fig. 7)of the solenoid 262. The solenoid is removably mounted on the bracket246 in the usual manner by an overlapping flange 248 at one end of thesolenoid base 'and a tongue and groove connection 256 at the otherendrof thev base, the latter being locked by a cam lever 252 (Figures 5and 29). When the solenoid is energized, its armature acts throughthe-lever 236 to pull the trigger 224 to the right. This rocks the searlever -2l4 and moves the scar out of the path of the firing key |138.The reason for the tongue and groove coupling between the trigger andthe trigger slide is apparent when it is remembered that the triggerrecoils with the gun and the lever carryingA the trigger slide ismounted on a member fixed to the cradle.

threaded into the forward end of the buffer housing. PressingV againstthek rear face of the disc 260 is a heavycompression spring 266' and alighter spring 268 nested within the heavy spring. Both springs areypre-loaded and are seated against the rear wall of the ,buffer-housing..Within the springs 266 and' 268 is a heavy snubber spring 2'16pre-loaded between the rear wall of the buffer housing and a flange 212on a sleeve 2141 which 'extends slidably through an aperture in therearend of.Y the housing and has' a circular nut. 216 screws-threaded ,ontthe: projecting? enctf portion and seated in arecess in the end of thehousing. i s

When the gun is red, the bolt |28 is kicked back by the combined actionof the thrust of the unlocking gas piston 18 acting through thetappets44 and slide H6, and the blow-back acting directly on the -bolt throughthe cartridge case. In normal `action the rear end `of the bolt strikesthedisc 260 of the buffer-forcing it back against the resistance Aof thespring 266 and 268 until the discjust reaches the forward end of thesleeve 214. The stored-up energy of the two springs then impels the boltforward to ram the fresh round which is fed into line with it during itsrebound from the buffer. In cases where there is excessive force in theblowback, due to an overcharged round or other causes, the bolt; willpush the disc 260 against the sleeve 214, compressing the snubber spring210, thus providing a yielding instead of a solid stcpior the'bolt whenits rearward velocity is higher than normal.

Charging mechanism The gun is charged for the initial .shotY by manuallyretracting the buffer` disc 268, moving the bolt back into contactwithit, then suddenly releasing the disc. A device for retracting thedisc is illustrated in Figure 15 and consists of a rod 218 which isthrust forward through the buffer from the rear end thereof. On theforward end of the rod is a key 280 `which passes througha keyhole 282in the center of the disc and turns 98 to lock the rod to the disc. Thekey 280 turns in a recess in the front face of the disc which, asindicated in Figure 16, is shaped to limit its turn to 90. The rear endportion of the rod 218, which projects beyond the rear end of the bufferhousing, is screw-threaded and is engaged by a nut 284 having `a tubularextension 286 to which is permanentlysecured a crank 288 and handle 298.Rotation of the nut 284 by `means of the crank 288 draws the rod 218toward therear. To take the reactive thrust of this pull, the nut 284 isarranged to bear against aball bearing assembly 292 mounted in a housing294, the forward edge of which fits into the clearance between theperiphery of the nut 216 and the wall of the recess in which it isseated. When the rod 218 and disc 260 have been retracted by operationof the crank 288 to compress the buffer springs suiiiciently, the disccan be released by turning the rod back until the key 280 registerswiththe hole 282. `For this purpose Ia slot 296 is provided in the rear endof the rod 218 to be engaged by an ordinary screw driver ifthe tubularextension 286 is left open at its rear end. As shown in Figure 15,however, a short screw driver blade298 is loosely mounted and'keyed inthe rear end of the nut extension 286. When the rod 218 is retracted`until it reaches the blade 298, the slot 296 receives the blade. Withthe blade held in engagement with the slot by the thumb of the operator,a 90 turn backwards allows the key 280 to release the disc 268.

Breechbloclc retracting mechanism To unload the gun, the breechblockmust be unlocked and retracted. VFor this purpose a retractor rod 300havingla grip 30| at its rear end is slidably fitted in a groove `in aside wall of the receiver (Figures 7 and 29) both rod and groove havinga square cross-section. The forward end portion of the rod 380 isslotted for about one third of its length. In the slot a `latch. 302 'ispivoted to the rod at 304 `(Figures '1 and 30).

The forward end of the latch 302 projects beyond the end of the rod 300and has a nose 306 adapted to engage in a vertical slot or recess 308 inthe breechblock slide I8 through an elongated slot 3|0 cut `through theremaining thickness of the receiver wall. A leaf spring 3|2 secured inthe rod 300 presses against the rear end 3| 4 of the latch 302 to pressthe nose 386 toward the recess 388. The nose is normally held out ofengagement with the recess by a retractor cover plate 3|6 which ishinged at 3|8 to the side of the receiver and has a button 328 on itsinner face normallypressing against the end 3|4 of the latch oppositethe spring 3|2. The cover plate 3|6 has a long shallow groove 322 in itsinner face in which a pawl 324 is pivoted at 326. A `leaf'spring 328 ismounted in the groove 322 behind the pawl to press it away from thecover 3|6. The cover 3|6 is normally secured against the side of thereceiver by a locking device shown in Figures and 28. Thisdevice islocated in a short L-eXtension 330 at the rear end of the cover 3|6which is horizontally notched to receive the rod 300 and is verticallydrilled for a locking assembly consisting of a vertical latch 332extending down from a crosshead 334 which normally rests on the uppersurface of the L- extension 330. A stop pin 336 is screw-threaded at itsupper end into the crosshead 334 and extends down through theL-extension 330. A head 338 on the stop pin limits the upward movementof the lock assembly. The latch 332 has two` notches adapted to receivea spring-pressed detent 348 so as to hold it in either its locked orunlocked position. In Figure 28 the locked position is shown wherein thebevelled lower end of the latch 332 projects into a hole in the uppersurface of the rod 380. When the lever is locked, the rod 308 isretained in its groove by a short tongue 34| (Figure 7).

To unload the gun, the pin head 338 is pressed `upward to elevate thelatch 332 clear of the rod y3 00; The retractor cover 3| 8 is then swungaway from the receiver. As it swings out, the nose 342 of the pawl 324is kept against the side of the rod 300 by the spring 328. The latch 382is also released to be rocked by the spring 3|2 to project its nose 386into the recess 308 in the slide ||6\.y When the cover 3|6 has beenswung ourl far enough for the pawl nose 342 to enter a notch 344 in theside of the rod 380, as indicatedfin broken lines in Figure 7, the coveris then swung back toward the receiver with a quick movement. The toggleaction of the pawl 324 and the portion of the cover 3|6 between the pawlpivot 326 and the cover hinge 3|8 forces the rod 300 to the rear,pulling the slide 6 with it. This unlocks the bolt which can then lberetracted by pulling on the grip 30|. If the cartridge case sticks whenit reaches the belt loop which it is to enter, the retractor cover 3|6can Ibe used as a jack to force the rod 380 rearward step by step. Forthis purpose a series of notches 346 are formed in the side of the rod.These can be successively engaged by the toe 342 of the pawl 324 byswinging the cover 3|6 on its hinge. The toggle action on the inwardswings results in a retracting force on the rod 300 greatly in excess ofthe input manual force. The rod retracts the slide H6, the bolt |28 andtheround engaged by the extractor |84.

Feed mechanism After the gun is red, the bolt and the empty cartridgecase are thrust rearward by gas pres` sure as soon as the breechblock isunlocked. The case enters its loop in the ammunition belt and isreleased by the extractor |84 just as the rear end of the bolt reachesthe buffer plate 26|). The momentum cf the bolt forces the plate backagainst the resistance of the buffer springs until the bolt reboundsforward. During this brief interval, the ammunition belt is fed forwardto move the empty case out of line with the bolt and to replace it witha fresh round in position to be rammed.

. The feed mechanism is actuated by reciprocation of the connecting rod7B, the forward and rearward strokes of this rod being caused by gaspressure on the piston 'Hl and by the spring f H0, respectively. Therear end of the rod 'I6 is screw-threaded into a rotor roll guide 348(Figures 3, 5, 9 and 42). A setscrew 35|) in the guide bears against aflat on the threaded end of the rod 16 to prevent the latter fromunscrewing. The roll guide has four rolls 3.52 mounted therein with asegment of each projecting from a side of the guide. The guide travelsin a longitudinal channel in the top of the rotor housing 353 (Figures35 and 41) which is a heavy block having a bore in which rotates thecylindrical rotor 356 and which is directly below the channel. for theguide 3&8. The side walls of the guide channel in the`rotor housing aregrooved to receive the projecting segments of the rolls 352. rA rollstud 358, is located on the median line of the guide 348 and projectsdown below it. On the lower end of the stud is a roll 36|) which ridesin a helical slot `362 in the rotor 356 (Figures 6 and V35) when thefeed is to be from the right. It is evident that reciprccation of theguide 358 results in oscillating rotation of the rotor 356 through alimited angle. The rotor 356 has another slot 364 with its helix in theopposite sense for use when feed from the left is desired. Ball bearings365 are employed at the ends of the rotor 356 to take the heavy axialthrusts on the rotor. Forward strokes of the guide 348 are limited by astop member 366. Rearward strokes are limited by the engagement of therear end of the slide with a raised portion 368 of the rotor housing 354(Figure 5).

The rotor 356 is keyed on a shaft 31D (Figure 3) which extends rearwardthrough a sprocket wheel 31.2 (Figures 34 and 39), which is free torotate thereon, and projects beyond the sprocket wheel. On thisprojecting rear portion of the shaft 31:0 a clutch member 3114 issplined adjacent to the sprocket wheel by means of a key 376 (Figures 3and 32) which is mounted in the shaft but has a radially projectingportion riding in an interior longitudinal slot in the clutch memberEVMV so as to permit free axial movement of the. clutch. The clutch ispressed resiliently against the rear end of the sprocket wheel by aspring 318 whichy surrounds a flanged thimble 380 on the shaft 310', theflange serving as a thrust washer pressed by the spring against the rearend of the clutch 3FM. The spring 3i8 is seated in andpartly enclosedbyl a housing 332 which is pinned to-the shaft 310;. The clutch 314 andits spring as,- sembly are contained in a housingl 38d (Figure 4;(1)which is rigidly secured to the rotor housing 35,4 by a pair of sideplates 385, 3,87 with the sprocket wheel 3'i2 between them (Figures 6,25, 32, 34 and' 35). These parts as thus assembled form a feed blockwhich canbe handled as a unit. The inclined edges 383 of the side platesof the f ,eed block (Figure 25) engage under complementary surfaces ofYa feed block 1ock 383 which. is

4bolted to the receiver key |168 to anchor therear end Aof the feedblock when in place (Figure 9), the forward end of the feed block havingan interlock (not shown) with the-sides of the receiver body.

The sprocket wheel 372 has at each end ve radial arms 390 spaced byarcuate recesses 392 shaped to fit against a cartridge case orthelforward portion of the bolt |29 (Figure 34). For indexing thesprocket wheel, five strong 'teeth 331i are formed on its rear face forengagement by teeth 395 on the clutch 3M. As indicated in `Figure 9, theteeth 356 on the sprocketwheel are squared on both sides, Whereas theteeth 39% on the clutch are sloping on one side and squared on theother. Thev sloping faces `cam the clutch away from the sprocket whenthe clutch is turned in one direction by the shaft Si@ but the squaredsides lock with the sprocket wheel teeth to drive the sprocket wheelwhen the clutch is turned in the other direction. The clutch has a setof t/eeth on each of its faces alternatively usable according to thedesired direction of feed The indexing of the sprocket wheel 3'F2 ispositively and accurately controlled by an escapsment latch (Figures 5and 17). The latch consists of a flat frame having side members withlateral tongues 462 thereon which slide in complementary grooves Mill inthe side plates 3523 and 555 (Figures 25, 32 and 34). The latch isformed with a loop yM36 at its rear end, and two cross members of whichthe forward member 568 has a releasing lug il-0 projecting forward and acamming lug M2 projecting rearward. As is evident from Figures 5 and 34,the latch dell is mounted in such a position that the cross member itilcomes between the two sets of sprocket arms 390 which are at the ends ofthe sprocket wheel Slg, and the lugs Alti) and M2 are so arranged thatone or the other is always in the path of a sprocket arm 3331 FigureV 5shows the sprocket wheel in its usual' position with one of the arms 330pressed against the stop lug MQ. To index the sprocket wheel, the latchlili? is moved' rearward to clear thestop lug al@ from the arm 398, thismov-ement of the latchv also-serving tobring the cam lug-M12 into thepath of the rear arms 330. As the sprocket wheel turns, a rear arm 390strikes the cam edge 41d of the lug fill-2l forcing the latch forward tobring the stop 'lug into the path of' the next successive arm at theforward end' of' the sprocket Wheelf to stopV the wheel afterl exactlyone-fifth of a revolution. The latch 400'- as shown in Figure 5 isadapted for feeding from the right hand? side of the gun. If it isdesired to feed from the left hand side, the latchl is simply turnedover so that the lugs tl-8 and M2 will facev the other way; l

When the gun is fired, the blow-back energy ofthe empty cartridge caseis utilized to*A kick the latch Miu to the rear so as' to release thesprocket wheel 312 for a feeding step. As shown f in Figure 12,thecartridge caseI strikes the lower dit with the openings 4260i and430a respectively,

in the top member of said housing (Figs. 5, 6, 9 and 40). The levershave teeth 432 and'434 respectively which mesh in opposed notches in theside members `oi the latch 408. Thus a forward thrust of the -upper end422 of the back stop 4I8 actsthrough-the lever` system to thrust thelatch468 rearward. This reversal of direc-v tion of movement by means ofthe lever system is for the rpurpose of avoiding premature unlocking ofthe sprocket Wheel by the inertia of the latch 400 during the recoil. Itis evident `from Figure 5 that the inertia of the latch tends to give ita forward thrust relative to the receiver, thus preventingaccidentalgunlocking of the sprocket arm 398 by displacement of thelocking lug 4in. Since the permissible movement of the latch 488 isdefinitely limited, the back stop 478 also serves to stop the rearwardtravel of the empty cartridge case when it reaches its proper positionin abelt link. s

The back stop 4I8 (Figures 9V, 171, 12 and 31) has a flat body disposedin a vertical planeand having a slot 4316 through which the pinr428 eX-tends. The slot is surrounded by a reinforcing rim oneach side. Theupper end `portion 422 of the back stop is thicker than'the body portionand is bevelled or rounded toi-lt in the loop 486 at the rear end of thelatch 45|).` At the lower end ofthe back stop the toe `4l6 is narrow androunded to ride in 4a small groove 438` in the forward portion of thebolt l2() (Figures 9, 12 and 18).. This'groove extends for about`onethird the length of the bolt and decreases in depthy from a maximumat the forward end of the bolt. When the bolt is forward,l the toe 416rides on topV of the bolt and holds the back-stop in its elevatedposition as shown in Figures 9 and l1. When the bolt moves rearward thetoe 4I6 is pressed into the groove 438 by a leaf spring 448 which issecured to the top` of the clutch housing 384 and bears upon the uppereX- tremity of the back-stop; By the time the forward end of the boltreaches the toe`4|6, the latter has moved down in thegroove into `thepath of the cartridge case which it stops and by which it is actuated.

Ammunition belt guide Ammunition is supplied to the gun by the usualmetal link belt which can be `fed in from either side, the feedingmechanism being arranged accordingly as hereinbefore described. Owing tothe rapid movementsof recoil and counter recoil which the gun assemblyhas relative to the cradle during bursts of continuous fire, guidingmeans for the portion of the belt approachingy the gun being` secured tothe cradle 54 by a bracket 446 (Figure 34), acts as a slide for theportion of the belt traveling between the chute 442 and the receiver.Extending from the receiver to the rear side wall of the chute 442 is aguide 458 for the rounds, this guide being constructed of` links securedtogether in sucha manner that the guide is flexible to a limited extentin a vertical plane, but inflexible in a horizontal plane. The guide ishinged to the `receiver at 452 and to the chute at 454. The guideconsists of two series of links 456 and 458 secured to each other instaggered relation. Between the twoseries are guide elementsy468 (Figure33), each of which is a short channel with inturned flanges 462 Whichenter the extractor grooves ofthe rounds when the latter leave the chute442. The guide assembly is held together by studs 464,'tw0 of which arewelded to each of the inner links 456. These studs extend through holesin the guide elements 468 and the outer links 458 and are secured byWashers 466 which are pinned on the projecting ends of 'the studs. Thechannel guide elements 458 guide the rounds into the receiver. A guide468 is also provided for the belt links so as to keep them properlyspaced from the bases of the rounds. This guide is secured to the sidewall of the receiver (Figure 34) and projects out a short distance. Thelower surface of the guide has a shallow groove 478 which is just Wideenough to receive the upper portions of the belt links, the sides of thegroove being flared at the'entering end to act as a camming fI-heprojectile ends of the rounds are guided into the receiver by a ramp 472Figure 35 which is`a substantial piece secured against the side of thereceiver with a thinner portion 474 extending-into the .receiver with acurved upper surface to guide thefprojectiles. A corresponding ramp 476is secured -on the opposite sideV of the gun for use when 'the feed isdesired in the other direction.

When th'erounds enter the receiver the cases are guided by' a rampspring 478 `which is a thin sheet of spring steel secured on the outsideof the receiver with a portion 488 bent to enter the receiver and -toserve as the guiding element. The guide portion 436 is preferably madewith large cut-outs to increase its resilience, that is, to reduce itsstiffness.` A corresponding ramp spring 482 is mounted on the other sideto guide the outgoing empty cartridge cases or to guide incoming' roundswhen the feed is from the left. This opposite ramp spring also serves asa stop for rounds fed" in from the right and thus acts with the rampspring 47S to align the round.

" Since the guide 458 for the rounds is effective' only up to the pointwhere the rounds enter the receiver, a guide extension is preferablyprovided to control the rounds up to the moment when they move intoalignment with the bolt and firing chamber. This could be in the form ofan upturned flange on the rear edge of the entering portion 480 of theramp spring 476, but as shown in Figures 8 and 34, a separate piece 484of spring metal may be secured outside of the ramp spring 478 with anupturned flange 486 on the rear edge extending into the receiver andarranged in line with the guide flange 462. This flange 486 rides in thegrooves of the rounds and prevents forward or rearward displacement ofthe rounds with respect to the gun until they are in position to berammed. A corresponding guide 488 is mounted on the opposite side.

Modified trigger mechanism A simplified form of trigger mechanism isshown in Figure 14. The sear 498 is the tip of the armature 492 of asolenoid 494 which is mounted Within the receiver to the rear of thereceiver key |68. The armature 492 is vertical and its tip engages theforward face of the ring pin key |48 when the armature moves to theposition shown in the figure. A spring 486 in the solenoid presses thearmature toward this position. The solenoid when energized serves as atrigger: to elevate: tliej armaturei and move the:

sear liverticalljf-f out roffthepatlil'of ftliefk'eyls` I 48:De-energizationf of? the solenoidpermitis` the; spring 4535 to movetliefsear downfinto the path of the key M8 andithus t'olpreventfurtlier-f'rng` Iy claim: 11. In a gunliaving witubeyacylindenhaving aport openingintoy said'ztub'e to admit ,nigh press sure gas intofsaid-zcylinder; means :'difivenafbyf: gasY pressure in said i cylnderffor; feedingaroundsisuce: cessively` into position: for'rainmingi, said;means including a sprocket :Wheelitoi-.receivee and `advanceA thesuccessive `rounds-f. an: escapemen'rr,latcli.nor-A mally locking-said;Wheel?, against `vmovement;.and`

means operable# byf. bloiwbacl; impact.Y of a1 car-1 fridge caseV tounlockf said wheel for as feeding.

3-` Inv a gun` having altube, normallyA locked i meansA operable by.,`gas` pressure Eroman-,intermediate point'. in saidV tube to` feed..successive,

rounds. intoy positionl for ramming, and. means;-

operable. by. blow-back impact, ofecartridgecases,

to unlock said-.lockeel-means'` fora feeding step.

4. Ir1y aA gun having atube; normally. locked' means operable by.A gaspressure/from anintera mediate point in.` saidv tube` tol feed;successive,

rounds intoposition forv ramming,v abolt recipe..

rocable to ram eachlroundwlien inposition and.

to extract the empty. case aft-er. ringysaid bolt havingfa longitudinalgroove in, the top. offthe. forward portion thereof, and. means forunlock.-

ing said feeding means forca feeding step', said.

unlocking means including an.' upright lever. liavfing, itslowerend.on.saidb01t, and adaptedton BE-EERENCES; GITED.'

The following references are of'recordf in' thej file vof'this patenti15 UNITEDf STAT-ES PATEN'ISy Nimber- Namel Dat-e- 55%",5043-l Benet`July 14; 189.6- 645536 Teaie\ Mar;- 13; 1900: .122903854 Sturgeon Jari.7', 1919' 9 0 1,323,025 Darne Nov.A 25, 1919VVA 1,502,259 Lucas-July-22; 1924i 157022063; SWebi-liusfl Feb;v 12,' 1929A 1135017522#McCann- M'ar. 18,-1930`- lj809i'222 Son'oni; Jurie-9; 19311',8-22l)79f=f Bullet al. S'ept; 8,*-193'1rv 2093705` BlWin'g Sept: 21;-1937 231442411' Eliane! Y- Jani 17; 1939 21495512? Eian'e f Marl. 7,1939y 2202,232 Ro'ssinanith 4 7- l\'/lay28;` 1940' ,0 231204.28@Williams'- June-11i` 1940l 2;#335'3854'1 Green -Dec, 7, 1943? 2l33f7,l5iBurton -D'ec. 2l, 1943?. 25339,@27f Mossoer'g Jan. 11, 1944l2?;35391'18'- Schirokauer f- 'J1l1ly. 4, 1944;' .5 21,*36534592D'obremys1. Dec.A 19;1944 Ruger I..... NOV. 2540123601 Cortey l f June1'1; 19,465 2,4-l1379l Rataiczak: Dec; 3, 1946 y FOREGN' PA'IENTS*Number A l Countryr4 Date;

12;2.06f Great- Britainf 1892,- 22459527 (rreat,v Britain MayA`249.1923; 190,057 Germany Scpih 27, 1907 45P 1931-4379 Switzerland Jan.17, 1,9381v rock said: lei/eri' and! meansl` movable a limited distanceeby said*L levertounlockftheV feeding meansy andl to1 cause"l the leverto -stopftherearf- Ward ltravel; offsaidf cartridge case at'f theiproper poi-nt? ferr lateralidischargelftliereof from the' gun.

WALEACE HALEILTONL

